It has long been the practice, when painting while standing on a ladder, to hang a container for paint or other brush spreadable liquid by its bail from a rung thus to enable the painter to hold onto the ladder with both hands while changing his position and then to be able to hold onto the ladder with one hand with the other hand free to dip the brush into the paint and spread the paint on the wall against which the ladder leans.
This practice had the obvious disadvantageous features that the suspended container was behind the ladder and free to swing and various proposals have been made to support the containers in more accessible positions. Such proposals include the concept of providing holders for the paint containers which have supports to be inserted into and in some cases through the tubular rungs of a metal ladder with the paint container supported at one side thereof.
None of these, as far as I am aware, has been well received with principal causes for their non-acceptance, production costs, inadequate support for the containers and their bulk making shipping costly and storage a problem.